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Care Guide: Daphnia

Living Care Information

Daphnia magna,
Daphnia pulex

commonly known as water fleas

Quick Start Information

  • Open the shipping container and remove and inspect the jar of Daphnia.

  • Unscrew the lid and rest it on top of the jar to allow air exchange that is vital to Daphnia survival.

    Note: Do NOT aerate the culture with a pipette. Do NOT screw the lid back on the jar.

  • Keep the culture jar in a cool area (21° C or 69° F) out of direct sunlight.

  • Daphnia can survive in the culture for 3 to 4 days without further care.

About the Organism

  • Daphnia are commonly known as water fleas.
  • Daphnia reproduce sexually and asexually.
  • Daphnia are filter feeders.
  • Female Daphnia produce a brood of eggs each time they molt.
  • Daphnia can produce resting eggs that can withstand harsh conditions.
  • Domain: Eukarya
  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Branchiopoda
  • Order: Cladocera
  • Family: Daphniidae
  • Genus: Daphnia
  • Species: magna or pulex


If you are planning on doing an experiment with the Daphnia, have them arrive as close to the procedure date as possible and have the experiment completed within two days.

The organisms should survive in the jar they are shipped in for 3 to 4 days—as long as the lid remains loose to allow for gas exchange. For most uses, no further care is needed.

Your shipment will contain at least 30 adults. Juveniles may also be present. Do not be alarmed while inspecting the culture if you notice debris that looks like dead Daphnia on the bottom of the jar. These are most likely exoskeletons shed by the organisms as they grow and molt. Live Daphnia will be swimming slightly above the bottom of the jar, where they settle if they experience shipping shock. They may also appear bright red in color due to shipping shock. Give your Daphnia 12 to 24 hours to recover and resume normal movement.


A culture of Daphnia can be maintained in any size container. We recommend containers with a volume of at least 1 gallon to house 100 Daphnia. We recommend using natural spring water or well water for culturing Daphnia. Municipal tap water sources may contain contaminants that can harm Daphnia.

You may also want to consider providing a supplemental light source for the Daphnia as exposure to light helps with reproduction. Daphnia typically reproduce well with 12 hours of light and 12 hours of darkness a day. Be sure that any artificial light does not significantly heat the water in the container.

The temperature of the water should remain near 70° F to promote successful breeding. The pH of the water should be maintained between 7 and 8.5.


Daphnia are filter feeders. They strain microscopic food particles from the water. Daphnia pellets, an algae food source, and a baker’s or brewer’s yeast suspension are all good feeding options for cultures.

To prepare a yeast suspension, add spring water to a clean 2-liter plastic bottle and stir in enough baker’s or brewer’s yeast to make the water appear milky. Store the suspension in a refrigerator and always agitate before use to resuspend the yeast. Add a few drops of this food to your culture each day. An alternative is to crush 3 to 4 grains of dry baker’s yeast on clean paper and dust this on the culture water’s surface. Hard-boiled egg yolk or powdered egg yolk can be used in the same amounts as yeast to encourage bacterial growth.

Avoid overfeeding as overgrowth of bacteria can cause oxygen depletion in the culture container.

Maintaining and culturing

Do not allow the culture water to become cloudy. Each week draw off and discard about 1/4 of the water. Replace it with fresh spring water. Do not use municipal tap water because Daphnia are extremely sensitive to the metal ions it contains. (Daphnia are so sensitive to metal contaminants that they are used to monitor the water quality of streams and lakes.)

Over time, debris will accumulate at the bottom of the container. The debris includes deceased organisms, discarded exoskeletons, and uneaten food. It may also include Daphnia eggs. Do not discard the debris.

Daphnia cultures are extremely sensitive to temperature, pH, and other water quality parameters. Cultures can and do fail suddenly. If you plan to maintain cultures of your Daphnia, we recommend that you maintain two or three separate populations to prevent complete loss.


We do not recommend releasing Daphnia or any other organism into the wild. When you have finished with your culture, you can use it as a food source for fish in a freshwater aquarium. To completely dispose of the culture, add bleach to the water and flush the contents of the container down the drain with plenty of water.


No Biosafety information needed for this organism.



    We just received our Daphnia and they are all on the bottom. Are they dead?

    Give them time to recover from shipping and to begin swimming. Remember that Daphnia grow by shedding their exoskeletons, and these accumulate on the bottom of the culture jar.

    I poured my Daphnia into an aquarium and they all floated. What went wrong?

    Daphnia have an expanded carapace that can retain air. When you poured them into the aquarium, air retained by their carapaces caused them to float and become trapped on the surface. Add Daphnia to an aquarium by gently submerging the open jar and pouring it out underwater to release them.

    We want to do a project on the heart rate of Daphnia. Which organism should we use?

    We recommend Daphnia magna for heart rate studies due to its larger size and slightly slower heart rate. For those studies, use the organisms as soon after you receive them as possible. See our video Observing Daphnia Heart Rate for more information.

    How can I tell male from female Daphnia?

    Most populations contain females, with few if any males. Female Daphnia have a dorsal egg sac that can be observed under a microscope during breeding season.

    Can I keep Daphnia in an aquarium with fish?

    You can, but the fish will eat them. Many aquarium hobbyists culture the organisms to feed their fish.

    Can I refrigerate Daphnia?

    We do not recommend refrigerating Daphnia. Keep them at normal room temperature. Plan to use the organisms as soon as possible after arrival.

    We tried to culture Daphnia. At first everything went well, but after several weeks, they all died. What went wrong?

    Daphnia populations will sometimes experience die-off. In most cases, the females leave behind eggs that will hatch and restart the culture. The eggs are among the debris at the bottom of the culture tank. It is best to maintain 2 to 3 separate cultures in case one of your cultures experiences die-off.

    Need help?

    We want you to have a good experience. Orders and replacements: 800.334.5551, then select Customer Service. Technical support and questions: caresheets@carolina.com

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